Parameters
112 M-Max Series Adjustable Frequency Drive MN04020003E—October 2013 www.eaton.com
Braking (P12)
In parameter group P12 you can set different brake functions:
●
DC braking
●
Generative braking (brake chopper)
●
Mechanical braking (actuation)
The brake functions allow you to reduce undesired coasting
and long coasting times. Mechanical braking also ensures
safe operating states.
DC Braking
With DC braking, the frequency inverter supplies the
three-phase stator winding of the three-phase motor with
DC current. This generates a stationary magnetic field which
in turn induces voltage in the rotor while the rotor is in
motion. As the electrical resistance of the rotor is very low,
even small induction can generate high rotor currents and
thus a strong braking effect.
As the speed decreases, the frequency of the induced
voltage reduces and therefore the inductive resistance also.
The ohmic resistance becomes more effective and thus
increases the braking effect. However, the generated braking
torque drops off abruptly before the rotor is at a standstill and
disappears completely as soon as the rotor movement has
ended.
DC braking is therefore not suitable for holding loads, nor for
intermediate braking. Once DC braking has been activated,
the motor comes to a standstill.
CAUTION
Debounced inputs may not be used in the safety circuit
diagram. DC braking results in additional heating of the
motor. Configure the brake torque, set via braking current
(P12.1) and the braking duration (P12.2 and P12.4), as low as
possible.
Braking
PNU ID
Access
RUN Value/Range Description
Factory Setting
(P1.3)
P12.1 507 X — DC braking, current I
e
0.2 x I
e
–2 x I
e
(A) Set value for the DC current, which supplies the motor
during the DC braking
The value depends on the rated operational current I
e
of the
frequency inverter
The parameter is only active, if a value >0 has been entered
for P12.2 or P12.4
P12.2 516 X — DC braking, braking time at start 0.00
0.00–600.00s The braking time of the DC braking [1] is activated with the
start command (FWD, REV)
Braking Time at Start
After the time set has elapsed, the frequency inverter
starts automatically with the acceleration time set at
P6.5. The speed of the motor [2] follows the
characteristic of the output frequency [3]
f
t
f
out
P12.2
f
P6.5
FWD
REV
1
2
3
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